1. Field of the Invention
The present invention generally relates to mechanical blood pumps. More specifically, the invention relates to biocompatible mechanical blood pumps for circulatory support of patients, particularly those in refractory cardiogenic shock.
2. Description of Related Technology
Cardiogenic shock occurs in a variety of clinical scenarios, including, but not limited to, acute myocardial infarction, viral myocarditis, massive pulmonary embolus, decompensated cardiomyopathy, and post cardiotomy failure. Without mechanical support, mortality is extremely high and has been reported to be from 40-80 percent. Although many patients die from multisystem organ failure, low cardiac output is likely the inciting event. The institution of circulatory support and restoration of end organ blood flow could potentially attenuate organ injury and reduce mortality.
A variety of ventricular assist devices (VADs), including blood pumps, are currently available or in clinical trials. Many of these devices are designed for intermediate or long term support, either as a bridge to heart transplantation or as destination therapy. Since these devices are implanted, they require extensive surgical procedures and are very expensive. Because of the expense and complexity of implantation, universal application of these devices to the majority of patients with cardiogenic shock is impractical.
One type of VAD, a roller pump, is frequently used in cardiopulmonary bypass and is always used in association with a venous reservoir, which ensures adequate filling of the pump. In the absence of a venous reservoir, as would be required for prolonged support, significant negative pressure (with catastrophic cavitation) can result during inadequate venous drainage. In addition, a sudden occlusion of the outflow limb of the pump will generate exceedingly high circuit pressures, risking tubing rupture. These features make roller pumps impractical for use as VADs, but they are often employed in extracorporeal membrane oxygenation (ECMO) systems, where trained perfusionists or other personnel typically oversee and operate the pump continuously. Although the disposable costs are low, labor costs for monitoring can make this type of support less cost effective.
As seen from the above, there is a need for a biocompatible, mechanical blood pump that can be used as a VAD to restore circulation in cardiogenic shock, and which is inherently safe, self regulating, nonthrombogenic, simple, durable for weeks, applicable for left, right, or bi-ventricular support, or ECMO, and for patients of any age or size. In addition, the device should be inexpensive and provide for monitoring and achieving optimal extracorporeal blood flow relative to patient fluid status.